Smart phones are typical examples of a product having a touch panel including a display device and a touch sensor. The touch sensor is formed to overlap with the display device, or incorporated in a pixel.
A touch sensor is arranged to overlap with sections which divide a screen of a display device into a plurality of pieces. By touching a position corresponding to the position of an icon displayed on the display device, a user inputs a command. Because a smart phone performs complicated processing, a user is supposed to have a smart phone always in his/her hand and operate it while viewing an image during its use. Accordingly, a touch panel needs to have a constant resolution.
Meanwhile, a command-input device which allows a user to operate without visual observation, such as an information guide terminal (a car navigation) to which a command is input in accordance with the number of touches is proposed (Patent Document 1).